FOOD FOR PLANTS 181 



recovered or won back in the crop/ As has already 

 been mentioned, these figures agree quite closely with 

 results reported from European countries, and they 

 also confirm earlier work carried out at this Station. 

 But even so, they are not satisfying figures. We at 

 once ask why there is this enormous loss of nitro- 

 gen and especially why the loss is so much greater 

 with the organic materials than with the Nitrate of 

 Soda and ammonium sulfate. If the loss is to be 

 attributed to the leaching out of the materials, then 

 it would seem that the figures should be reversed. 

 Unquestionably, a certain amount of loss takes place 

 in this way, but this cannot explain the loss of over 

 two-thirds from the manure against a little more 

 than one-third from Nitrate. 



It is well known that organic materials must 

 undergo certain transformations in the soil before 

 the nitrogen can become available, and it seems that 

 during these transformations nitrogen as ammonia, 

 Nitrate or as elemental nitrogen must be lost in con- 

 siderable quantities. As bearing on this it may be 

 pointed out that Russell and Richards (5) have 

 shown by laboratory experiments with manure that 

 in addition to the loss of ammonia by volatilization 

 there is still a loss amounting to 15 per cent, or more 

 of total nitrogen, and they have gone further and 

 shown that during decomposition there is an evolu- 

 tion of gaseous nitrogen. This they believe com- 



^ Or if we assign to Nitrate nitrogen a value of 100, then the relative 

 availability of the four materials stands as follows: 



Nitrate of soda 100.0 



Ammonium sulfate 76. 1 



Dried blood 62.0 



Manure 52.4 



